Blurry applications Dell Inspiron 7520 after windows 8.1 upgrade

After the upgrade, the switchable GPUs didn't work and many applications have a different (and blurry) resolution compared with the rest of the screen. All the Dell video drivers (even the drivers for windows 8.1) didn't solve the problem.

I solved the switchable GPU issue installing the latest video drivers, taken directly from Intel and AMD websites:

- for the Intel HD 4000: driver 10.18.10.3277, 8-19.2013

- for the AMD Radeon 7730: driver 14.501.1003.0, 11-20-2014.

This is the only combination of drivers that works (I tried many...) but the blurry applications' issue is still unsolved. Look at the picture in the link below (the resolution of the screen is ok, while the words in the window are blurry).